Analysis of a gene structure has progressed remarkably in recent years. A number of gene structures including human genes have been revealed. For the analysis of a gene structure, a DNA microarray including biochips is used, where a solution containing thousands to millions of different DNA strands are aligned and immobilized as microspots on a carrier or a base such as a slide glass.
Such a microarray has been produced using an ink-jetting method in view of its high speed spot-formation action and uniform spot quality.
PCT International Patent Publication No. 02/90984 discloses a method of producing a biochip including a plurality of spots containing a plurality of liquid samples arranged with high density. This method includes the steps of providing a discharge unit comprising a body or a substrate and a piezoelectric/electrostrictive element; the body including an inlet, a channel, a cavity or a reservoir, and an outlet; introducing a liquid sample into the cavity through the inlet; disposing the carrier or the base at a position opposing the outlet; discharging the liquid sample introduced into the cavity from the outlet as small volume liquid drops to form a spot on the carrier or the base; and repeating the above steps for a plurality of liquid samples. According to this method, when using the discharge head including one or more discharge modules having one or more discharge units, at least one of a plurality of liquid samples is introduced into the cavity through the inlet of the discharge unit so that one liquid sample is provided in one discharge unit respectively. One or more trays on which one or more carriers or bases are fixed are removably mounted on a table and moved thereon to a discharge position of the discharge unit corresponding to a predetermined position of the carrier or the base. Each liquid sample introduced into the cavity is discharged to the predetermined position of the carrier or the base as liquid drops to arrange spots containing a plurality of liquid samples on the carrier or the base with high density. This method provides the advantage that the spots are formed with high definition in a short time.